/*
 * @Date: 2021-09-07 19:44:03
 * @Author: Acckno1
 * @LastEditTime: 2021-09-07 20:07:34
 * @Description: 
 */
#include <iostream>
#include <cstring>
#include <algorithm>
#include <cstdio>
#include <cmath>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <set>
#include <bitset>
#include <utility>
using namespace std;

#define mm(a, n) memset(a, n, sizeof a)
#define mk(a, b) make_pair(a, b)

const double eps = 1e-6;
const int INF = 0x3f3f3f3f;

typedef long long LL;
typedef unsigned long long ULL;
typedef pair<int, int> PII;
typedef pair<double, double> PDD;
typedef pair<LL, LL> PLL;
typedef pair<int, LL> PIL;

inline void quickread() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
}

unordered_map<int, int> mp;
set<int> st;
int n, m;

inline void solution() {
    cin >> n;
    for (int i = 1; i <= n; i ++ ) {
        int a, b;
        cin >> a >> b;
        mp[b] = a;
        mp[a] = b;
    }
    
    cin >> m;
    for (int i = 1; i <= m; i ++ ) {
        int k; cin >> k;
        st.insert(k);
    } 

    vector<int> res;
    for (auto & s : st) {
        if (st.find(mp[s]) == st.end()) {
            res.push_back(s);
        }
    }

    
    if (res.size()) {
        printf("%d\n%05d", (int)res.size(), res[0]);
        for (int i = 1; i < (int)res.size(); i ++ ) printf(" %05d", res[i]);
    } else {
        printf("0");
    }
    
}

int main() {
    freopen("input.txt", "r", stdin);
    quickread();
    solution();
    return 0;
}